By Stamatis Kalogiannis |
| Male Erhard's Wall Lizard. The typical blue outer ventral scales are visible. Southwestern Alonissos, July 2020 |
Short introduction
Out of the several lacertids of Greece, the most iconic one has to be the Erhard's Wall Lizard, which could be described as living proof of evolution. This small, but gorgeous and highly variable lizard is present in a large part of the mainland and on most of the Aegean islands. Since the early 20th century, numerous subspecies have been described from the Aegean region, based almost exclusively on morphology. Although this species does indeed present a huge diversity when it comes to morphology, most of these subspecies are questionable, with only about six main preliminary groups; P. erhardii ssp. riveti (Balkan peninsula, including Northern Greece), P. erhardii ssp. ruthveni (Northern Sporades) - which is very similar to ssp. riveti -, P. erhardii ssp. livadiaca (Central Greece [incl. Attica], Euboea & a part of the P eloponnese peninsula) as well as three separate groups in the southern Aegean (western Cyclades, central Cyclades and southeastern Aegean islands). A future split is a very possible scenario, as it has already happened in the case of the Pori Wall Lizard (Podarcis levendis) and the Cretan Wall Lizard (Podarcis cretensis).
Podarcis erhardii on Alonissos
On Alonissos, the Erhard's Wall Lizard inhabits a large selection of biotopes and is even present on tiny islets with little vegetation. It is widely distributed throughout all of the island and almost every islet of the Alonissos Marine Park. The subspecies described from the area, ssp. ruthveni, presents a big variability in coloration, with the most abundant colors being olive, brown and green in both sexes. This lizard inhabits most of the habitat types, can be seen throughout the whole year (also active during warm winter days), and is with no doubt the most commonly encountered reptile species on the island. It feeds on a variety of invertebrates, whereas on small islets it lives alongside the Eleonora's falcon, where it feeds on parasites and flies attracted to prey leftovers and excrement. Can often be seen basking on stonewalls, climbing on small trees or running between scrubs. Less shy than the other lacertid of the island, the Balkan Green Lizard.
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| Large male with a typical early spring coloration. SW Alonissos, February 2021. |
Territorial behavior and mating
Competition on reproduction and food can be very intense - males of the Erhard's Wall Lizard are extremely territorial and may defend their grounds against rival males with aggressive and violent conflicts, some of which result in fatal injuries and limb losses. Mating takes place in spring (February to May). Copulation begins with the male biting the tail of the female. Pairs might stay close to each other for a short period of time and can be observed thermoregulating together, although it is not very clear whether this behavior indicates actual pair bond.
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| Pair; female (left) and male (right) basking on the same spot. SW Alonissos, March 2020. |
Habitat selection
This lizard typically occupies a wide range of sunny habitats, ranging from rocky, coastal habitats with low phrygana or dry areas with dense maquis, to cultivated land with stonewalls as well as dry forests with clearings. Generally, the presence of the species is associated with stonewalls, scrubs and safe thermoregulation spots.
Sexual dimorphism and color diversity
As in most lacertids, females and males of P. erhardii ruthveni differ significantly, both in coloration and size. Males are generally bigger, with larger heads and typically reticulated dorsal and lateral patterns, which are usually a mix of black, olive, brown, green and sometimes yellow spots in the lateral area. In addition, blue ventrolateral flanks, yellow or reddish bellies and colorful necks consisting of yellow or light orange/reddish often occur during the breeding season. In the winter, most males are greenish/olive colored with less colorful patterns. Females are usually more pale, with an olive, brown or green coloration and clear dorsolateral stripes, sometimes bordered by dark patches. The lateral area of females is often darker than the dorsal coloration. Although females generally exhibit pale white necks, some may have a reddish coloration in the neck area, similar to that of males. Juveniles are brown or olive colored with visible dorsolateral stripes, often bordered by a faded pattern. Concolor morphs - a morph in which lizards do not exhibit any pattern, markings or stripes but are uniformly colored - are not extremely rare on the island, although not frequently observed. One documented case from Alonissos is described here; https://www.researchgate.net/publication/350387293_A_concolor_morph_in_Podarcis_erhardii_ruthveni_Werner_1930_from_Alonissos_Greece
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| Colors present in the neck area of male individuals during the breeding season. |
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| Female exhibiting orange color in the neck area. SW Alonissos, March 2021. |
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| Male with a pale throat but with red in the ventral area. SW Alonissos, May 2020. |
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| Male exhibiting yellow in the neck area. Blue outer ventral scales are also visible. SW Alonissos, March 2020. |
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Male with a reddish coloration in the neck area. SW Alonissos, March 2020.
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| Typical female. Central Alonissos, March 2020. |
Additional highlights
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Caudal autotomy is a common and effective defense mechanism occuring in many lizard species. SW Alonissos, March 2021.
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| Tail bifurcation is a deformation that might occur after an incomplete autotomy. SW Alonissos, March 2020. |
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| Parasites on the front leg and dorsal area of a dead Podarcis erhardii. Parasitic infections are rather common on reptiles on Alonissos. |
